FORM FIVE SELECTIONS 2021** FORM 5 JOINING INSTRUCTIONS
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Slope map can be obtained in a variety of ways:
i) Direct field measurements using
inclinometer or by leveling.
ii) From contour map (not so accurate), as contour
data does not reflect the ground form exactly, it is okay only for general
planning purposes.
iii) Photogrammetry – stereoscopic
measurements from aerial photographs.
vi) Digital terrain modeling procedures using
computer.
b) Mapping
surface materials
Include mapping of
solid rocks and superficial deposits (soil, weathered and transported
sediments). It covers mapping of surface lithology and mega structures such as
faults, fold axis, joints etc depending on the requirement. For problem –
oriented map, more detailed information are recorded and presented eg.
Porosity, permeability, shear strength, degree of weathering, mineral
composition etc. The map produced is called morphographic
map.
Problem-oriented maps are used
for different purposes such as:
● Search for local
construction materials
● Evaluation of
foundation condition
● Slope stability
analysis
a)
Mapping
geomorhological processes
It is rarely to record the
actual process. What is recorded is an interpretation of forms and materials
associated with a defined process. The map produced is called morphogenetic
/dynamic map.
Examples:
● landsliding as a
process is not mapped instead landslide features are the one mapped. The same
applies to flooding, what is mapped is limits of past flood or margins of a
flood plain.
● Coastal
processes are not mapped, but tidal ranges, the dominant wave directions,
erosive features, etc are mapped.
● Erosion is not
mapped what is mapped is features associated with wind/water erosion such
as gullies, faceted pebbles and
boulders.
Based
on these mapped features causative geomorphic processes can be interpreted or
deduced. For example, the presence of deflation hollows, sand and silt mounds
around vegetation, this is indication of general potential of wind erosion in
the area. The presence of gullies is a sign of water erosion problem.
d) Mapping of
the age of landforms
It is very difficult to determine the actual age of
the landforms unless there are specific evidence such as C14 dates,
fossil or archaeological evidence.
Sometimes memory of local inhabitants can be used or presence of
historical records. Also age can be assigned on the basis of reference aspect
such as El nino, glaciation, climatic changes. It is commonly done in Europe
and America. The map produced is called morphochronological
map
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